diff --git a/packages/chat-client/src/components/ProjectModal.jsx b/packages/chat-client/src/components/ProjectModal.jsx
index bf63b22..71adef5 100644
--- a/packages/chat-client/src/components/ProjectModal.jsx
+++ b/packages/chat-client/src/components/ProjectModal.jsx
@@ -6,6 +6,7 @@ export default function ProjectModal({ project, mode, onSave, onDelete, onClose
   const [name, setName] = useState(project?.name ?? '');
   const [description, setDescription] = useState(project?.description ?? '');
   const [colour, setColour] = useState(project?.colour ?? COLOURS[0]);
+  const [systemPrompt, setSystemPrompt] = useState(project?.system_prompt ?? '');
   const inputRef = useRef(null);
 
   useEffect(() => {
@@ -15,13 +16,20 @@ export default function ProjectModal({ project, mode, onSave, onDelete, onClose
   function handleSubmit() {
     const trimmed = name.trim();
     if (!trimmed) return;
-    onSave({ name: trimmed, description: description.trim() || null, colour, icon: null, isolated: 1 });
+    onSave({
+      name: trimmed,
+      description: description.trim() || null,
+      colour,
+      icon: null,
+      isolated: 1,
+      system_prompt: systemPrompt.trim() || null,
+    });
     onClose();
   }
 
   function handleKeyDown(e) {
-    if (e.key === 'Enter' && mode !== 'confirm-delete') handleSubmit();
     if (e.key === 'Escape') onClose();
+    // Don't submit on Enter — textarea fields make Enter ambiguous
   }
 
   return (
@@ -35,7 +43,8 @@ export default function ProjectModal({ project, mode, onSave, onDelete, onClose
         background: 'var(--bg-surface)',
         border: '1px solid var(--border)',
         borderRadius: 'var(--radius-lg)',
-        padding: '24px', width: '380px',
+        padding: '24px', width: '420px',
+        maxHeight: '90vh', overflowY: 'auto',
         display: 'flex', flexDirection: 'column', gap: '16px',
       }}>
         {mode === 'confirm-delete' ? (
@@ -122,6 +131,32 @@ export default function ProjectModal({ project, mode, onSave, onDelete, onClose
               </div>
             </div>
 
+            {/* System Prompt */}
+            <div className="flex-col" style={{ gap: '6px' }}>
+              <label className="label-upper">
+                System Prompt <span style={{ opacity: 0.5 }}>(optional)</span>
+              </label>
+              <p className="text-xs text-muted" style={{ marginTop: '-2px' }}>
+                Overrides the global system prompt for conversations in this project.
+                Leave blank to use the global default.
+              </p>
+              <textarea
+                value={systemPrompt}
+                onChange={e => setSystemPrompt(e.target.value)}
+                placeholder="You are a helpful assistant specialised in..."
+                rows={4}
+                style={{
+                  background: 'var(--bg-elevated)', border: '1px solid var(--border)',
+                  borderRadius: 'var(--radius-md)', padding: '8px 12px',
+                  color: 'var(--text-primary)', fontSize: '13px', outline: 'none',
+                  width: '100%', resize: 'vertical', fontFamily: 'inherit',
+                  lineHeight: '1.6',
+                }}
+                onFocus={e => e.target.style.borderColor = 'var(--accent)'}
+                onBlur={e => e.target.style.borderColor = 'var(--border)'}
+              />
+            </div>
+
             <div className="flex" style={{ gap: '8px', justifyContent: 'flex-end' }}>
               <button className="btn-reset text-base text-muted"
                 onClick={onClose}
diff --git a/packages/chat-client/src/components/ProjectView.jsx b/packages/chat-client/src/components/ProjectView.jsx
index 493984d..062fddb 100644
--- a/packages/chat-client/src/components/ProjectView.jsx
+++ b/packages/chat-client/src/components/ProjectView.jsx
@@ -36,9 +36,9 @@ export default function ProjectView({ project, onNavigate, onBack, onSelectSessi
     }
   }
 
-  async function handleSave({ name, description, colour, icon, isolated }) {
+  async function handleSave({ name, description, colour, icon, isolated, system_prompt }) {
     try {
-      await updateProject(project.id, { name, description, colour, icon, isolated });
+      await updateProject(project.id, { name, description, colour, icon, isolated, system_prompt });
       onProjectsChange?.();
       setModal(null);
     } catch (err) {
diff --git a/packages/chat-client/src/components/SettingsView.jsx b/packages/chat-client/src/components/SettingsView.jsx
index e2de166..db5e76f 100644
--- a/packages/chat-client/src/components/SettingsView.jsx
+++ b/packages/chat-client/src/components/SettingsView.jsx
@@ -1,10 +1,10 @@
 import React, { useState, useEffect, useCallback } from 'react';
 import { useSettings } from '../hooks/useSettings';
 import { useModels } from '../hooks/useModels';
-import { getServiceHealth } from '../api/orchestration'; // ← merged
+import { getServiceHealth } from '../api/orchestration';
 
 export default function SettingsView({ onNavigate, onBack, modelProps }) {
-  const { settings, saveSetting, saving } = useSettings(); // ← single source
+  const { settings, saveSetting, saving } = useSettings();
 
   return (
     <div style={{ display: 'flex', flexDirection: 'column', flex: 1, overflow: 'hidden', background: 'var(--bg-base)' }}>
@@ -51,12 +51,16 @@ export default function SettingsView({ onNavigate, onBack, modelProps }) {
         </SettingsSection>
 
         <SettingsSection title="Models">
-          {/* ← Error boundary wraps ModelsSection only */}
           <SettingsSectionErrorBoundary>
-            <ModelsSection settings={settings} saveSetting={saveSetting} saving={saving} modelProps={modelProps}/>
+            <ModelsSection settings={settings} saveSetting={saveSetting} saving={saving} modelProps={modelProps} />
           </SettingsSectionErrorBoundary>
         </SettingsSection>
 
+        {/* Global system prompt */}
+        <SettingsSection title="Behaviour">
+          <SystemPromptSetting settings={settings} saveSetting={saveSetting} saving={saving} />
+        </SettingsSection>
+
         <SettingsSection title="About">
           <SettingsRow
             label="Service Health"
@@ -79,7 +83,8 @@ export default function SettingsView({ onNavigate, onBack, modelProps }) {
   );
 }
 
-// Error boundary — class component required by React for this pattern
+// ── Error boundary ───────────────────────────────────────────
+
 class SettingsSectionErrorBoundary extends React.Component {
   constructor(props) {
     super(props);
@@ -107,6 +112,8 @@ class SettingsSectionErrorBoundary extends React.Component {
   }
 }
 
+// ── Layout components ────────────────────────────────────────
+
 function SettingsSection({ title, children }) {
   return (
     <div style={{ marginBottom: '32px' }}>
@@ -125,11 +132,28 @@ function SettingsSection({ title, children }) {
   );
 }
 
+function SettingsRow({ label, description, action }) {
+  return (
+    <div style={{
+      display: 'flex', alignItems: 'flex-start', justifyContent: 'space-between',
+      padding: '14px 16px',
+      borderBottom: '1px solid var(--border)',
+    }}>
+      <div style={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
+        <span className="text-sm" style={{ color: 'var(--text-primary)', fontWeight: 500 }}>{label}</span>
+        {description && <span className="text-xs text-muted">{description}</span>}
+      </div>
+      <div style={{ flexShrink: 0, marginLeft: 16 }}>
+        {action}
+      </div>
+    </div>
+  );
+}
+
 function NumberSetting({ label, description, value, min, max, step = 1, onSave, saving }) {
   const [local, setLocal] = useState(value ?? '');
   const isDirty = local !== '' && Number(local) !== value;
 
-  // Sync when settings load from API
   useEffect(() => {
     if (value !== undefined) setLocal(value);
   }, [value]);
@@ -168,30 +192,78 @@ function NumberSetting({ label, description, value, min, max, step = 1, onSave,
   );
 }
 
-function SettingsRow({ label, description, action }) {
+function ComingSoon() {
+  return <span className="text-xs text-muted" style={{ fontStyle: 'italic' }}>Coming soon</span>;
+}
+
+// ── System prompt setting ────────────────────────────────────
+
+function SystemPromptSetting({ settings, saveSetting, saving }) {
+  const [local, setLocal] = useState(settings?.systemPrompt ?? '');
+  const [savedPrompt, setSavedPrompt] = useState(settings?.systemPrompt ?? '');
+
+  useEffect(() => {
+    if (settings?.systemPrompt !== undefined) {
+      setLocal(settings.systemPrompt ?? '');
+      setSavedPrompt(settings.systemPrompt ?? '');
+    }
+  }, [settings?.systemPrompt]);
+
+  const isDirty = local !== savedPrompt;
+
+  async function handleSave() {
+    await saveSetting('systemPrompt', local.trim() || null);
+    setSavedPrompt(local);
+  }
+
   return (
-    <div style={{
-      display: 'flex', alignItems: 'flex-start', justifyContent: 'space-between',
-      padding: '14px 16px',
-      borderBottom: '1px solid var(--border)',
-    }}
-      // Remove bottom border on last child via CSS would need a class;
-      // easiest to just let it render — the section border-radius clips it cleanly
-    >
-      <div style={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
-        <span className="text-sm" style={{ color: 'var(--text-primary)', fontWeight: 500 }}>{label}</span>
-        {description && <span className="text-xs text-muted">{description}</span>}
-      </div>
-      <div style={{ flexShrink: 0, marginLeft: 16 }}>
-        {action}
+    <div style={{ padding: '14px 16px', borderBottom: '1px solid var(--border)' }}>
+      <div style={{ display: 'flex', alignItems: 'flex-start', justifyContent: 'space-between', marginBottom: '8px' }}>
+        <div style={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
+          <span className="text-sm" style={{ color: 'var(--text-primary)', fontWeight: 500 }}>
+            System Prompt
+          </span>
+          <span className="text-xs text-muted">
+            Default instruction given to the model on every request. Projects can override this.
+          </span>
+        </div>
+        {isDirty && (
+          <button
+            className="btn-primary"
+            style={{ padding: '5px 12px', fontSize: '12px', flexShrink: 0, marginLeft: '16px' }}
+            disabled={saving}
+            onClick={handleSave}
+          >
+            {saving ? 'Saving…' : 'Save'}
+          </button>
+        )}
       </div>
+      <textarea
+        value={local}
+        onChange={e => setLocal(e.target.value)}
+        rows={5}
+        style={{
+          width: '100%',
+          background: 'var(--bg-elevated)',
+          border: '1px solid var(--border)',
+          borderRadius: 'var(--radius-md)',
+          padding: '10px 12px',
+          color: 'var(--text-primary)',
+          fontSize: '13px', lineHeight: '1.6',
+          resize: 'vertical', fontFamily: 'inherit',
+          outline: 'none', boxSizing: 'border-box',
+        }}
+        onFocus={e => e.target.style.borderColor = 'var(--accent)'}
+        onBlur={e => e.target.style.borderColor = 'var(--border)'}
+      />
+      {!isDirty && local && (
+        <p className="text-xs text-muted" style={{ marginTop: '6px' }}>Saved</p>
+      )}
     </div>
   );
 }
 
-function ComingSoon() {
-  return <span className="text-xs text-muted" style={{ fontStyle: 'italic' }}>Coming soon</span>;
-}
+// ── Service health ───────────────────────────────────────────
 
 function ServiceHealth() {
   const [services, setServices] = useState(null);
@@ -242,25 +314,18 @@ function ServiceHealth() {
               borderBottom: i < services.length - 1 ? '1px solid var(--border)' : 'none',
               background: 'var(--bg-elevated)',
             }}>
-              {/* Status dot */}
               <div style={{
                 width: 8, height: 8, borderRadius: '50%', flexShrink: 0,
                 background: svc.status === 'healthy' ? '#2ecc71' : '#e74c3c',
               }} />
-
-              {/* Label */}
               <span className="text-sm" style={{ minWidth: 90, color: 'var(--text-primary)' }}>
                 {svc.label}
               </span>
-
-              {/* Detail — show model for inference, nothing extra for others */}
               <span className="text-xs text-muted" style={{ flex: 1 }}>
                 {svc.key === 'inference' && svc.detail?.model
                   ? svc.detail.model
                   : svc.status === 'unreachable' ? 'Unreachable' : ''}
               </span>
-
-              {/* Latency */}
               <span className="text-xs text-muted" style={{ flexShrink: 0 }}>
                 {svc.latency}ms
               </span>
@@ -272,11 +337,12 @@ function ServiceHealth() {
   );
 }
 
+// ── Models section ───────────────────────────────────────────
+
 function ModelsSection({ settings, saveSetting, saving, modelProps }) {
   const { models, selectedModel, setSelectedModel } = useModels();
   const [selectedInfo, setSelectedInfo] = useState(null);
 
-  // Sync info panel when selection changes
   useEffect(() => {
     const m = models.find(m => m.value === selectedModel);
     setSelectedInfo(m ?? null);
@@ -287,7 +353,7 @@ function ModelsSection({ settings, saveSetting, saving, modelProps }) {
       <SettingsRow
         label="Models Folder"
         description="Path to folder containing .gguf files"
-        action={<ModelsFolderSetting settings={settings} saveSetting={saveSetting} saving={saving}/>}
+        action={<ModelsFolderSetting settings={settings} saveSetting={saveSetting} saving={saving} />}
       />
       <NumberSetting
         label="Temperature"
@@ -297,7 +363,6 @@ function ModelsSection({ settings, saveSetting, saving, modelProps }) {
         onSave={val => saveSetting('temperature', val)}
         saving={saving}
       />
-
       <NumberSetting
         label="Repeat Penalty"
         description="Penalises repeated tokens — higher reduces repetition (1–2)"
@@ -343,7 +408,6 @@ function ModelsSection({ settings, saveSetting, saving, modelProps }) {
         }
       />
 
-      {/* Model info panel */}
       {selectedInfo && (
         <div style={{
           margin: '0', padding: '14px 16px',
@@ -360,7 +424,9 @@ function ModelsSection({ settings, saveSetting, saving, modelProps }) {
             )}
             <InfoLine
               label="Context"
-              value={modelProps ? `${modelProps.contextWindow.toLocaleString()} tokens` : '—'}
+              value={modelProps?.contextWindow
+                ? `${modelProps.contextWindow.toLocaleString()} tokens`
+                : '—'}
             />
             <InfoLine
               label="Loaded"
diff --git a/packages/chat-client/src/components/Sidebar.jsx b/packages/chat-client/src/components/Sidebar.jsx
index 3c44909..bb7e6e7 100644
--- a/packages/chat-client/src/components/Sidebar.jsx
+++ b/packages/chat-client/src/components/Sidebar.jsx
@@ -104,7 +104,6 @@ export default function Sidebar({
   }
 
   const sessionRowProps = (session) => ({
-    key: session.external_id,
     session,
     isActive: activeSession?.external_id === session.external_id,
     isHovered: hoveredId === session.external_id,
@@ -236,7 +235,7 @@ export default function Sidebar({
                       </span>
                     </div>
                     {projectSessions.map(session => (
-                      <SessionRow {...sessionRowProps(session)} />
+                      <SessionRow key={session.external_id} {...sessionRowProps(session)} />
                     ))}
                   </div>
                 );
@@ -251,7 +250,7 @@ export default function Sidebar({
                     </div>
                   )}
                   {unassigned.map(session => (
-                    <SessionRow {...sessionRowProps(session)} />
+                    <SessionRow key={session.external_id} {...sessionRowProps(session)} />
                   ))}
                 </>
               )}